JPH04133113A - Constant-current circuit and oscillation circuit - Google Patents

Abstract

PURPOSE:To curtail the hardware quantity and the power consumption and to reduce the cost by varying smoothly a current value and an oscillation frequency allowing them to follow a power supply voltage, in a miniature/low power consumption device such as a note personal computer. CONSTITUTION:When a value of a power supply voltage Vcc is V4, voltage dividing resistances R2, R3 of a differential amplification input part 4 are adjusted so that an input voltage V2 of a differential amplifying part 3 becomes equal to a constant-voltage V1 of an output of a reference voltage part 1. In this case, a current I3 flowing through R4 is '0'. Subsequently, when the power supply voltage rises and comes to V2>V1, I3 flows to the VA side from the VB side. On the other hand, when the power supply voltage drops and comes to V2<V1, I3 flows to the VB side from the VA side. That is, when Vcc increases by setting Vcc=V4 as a boundary, I2 increases, and when Vcc decreases, I2 also decreases. Inclination of this characteristic is varied by a value of R4.

Description

[Detailed Description of the Invention] [Summary] This invention relates to a constant current circuit whose t current value can be controlled by a power supply voltage, and an oscillation circuit configured using this constant current circuit.

The purpose is to provide a simple circuit configuration for smoothly changing the constant current value and oscillation frequency depending on the power supply voltage. Each emitter is coupled with a resistor, the base of the first transistor is connected to a constant voltage source, the base of the second transistor is connected to a voltage dividing point of the power supply voltage,
a constant current circuit in which the collector current of the second transistor is controlled at a constant current according to the magnitude of the 1 tat pressure;
This constant current circuit is used as a charging circuit for a capacitor, and has an oscillation circuit that performs oscillation by switching charging and discharging.

[Industrial Application Field] The present invention relates to a constant current circuit whose current value can be controlled by an IT power supply voltage, and an oscillation circuit configured using this constant current circuit.

The oscillation circuit according to the present invention is useful for a variable frequency clock device in a battery-powered computer.

In battery-powered computers, high-speed operation is not required before entering an arithmetic processing mode, for example, when selecting a mode, so measures are taken to reduce power consumption by lowering the operating voltage. In addition, in conjunction with this, the oscillation frequency of the two oscillators is also lowered, since the clock speed may be lower, thereby significantly reducing power consumption.

[Conventional technology]

Conventional computers typically use fixed frequency oscillators as clock devices. Therefore, if it is necessary to make the clock frequency variable, multiple oscillators with different frequencies are provided.

There have been methods of arbitrarily selecting one of them, or methods of providing one oscillator with a relatively high frequency, dividing its output into a plurality of frequencies, and arbitrarily selecting the required frequency.

As such, many oscillators for lock generation are of the type that uses charging and discharging of capacitors.A typical circuit is to charge a capacitor with the power supply voltage through a constant current circuit, and to set the terminal voltage of the capacitor. When the terminal voltage of the capacitor reaches a certain level, the capacitor is discharged, and when the terminal voltage of the capacitor drops to another certain level, the discharge is stopped and the charging is restarted.This operation is repeated, and a sawtooth wave is generated.

However, in either case, a problem arises in that the number of hardware circuits such as three oscillators and selection circuits increases significantly.

[Problem to be solved by the invention]

An object of the present invention is to provide a simple circuit configuration for smoothly changing the constant current value and the oscillation frequency depending on the tag pressure.

[Means to solve the problem]

The present invention provides two oscillator capacitor charge/discharge cycles if
In order to change the f voltage depending on the voltage, the constant current circuit that supplies the charging current to the capacitor is made to have dependence on the power supply voltage.

Fig. 1 is a basic configuration diagram of a constant current circuit based on the present invention, Fig. 2
The figure is a diagram showing the principle configuration of an oscillation circuit using the constant current circuit of FIG. 1.

In FIG. 1 and FIG. 2, 1 is a reference voltage section.

2 is a constant current source section, 3 is a differential amplification section, 4 is a differential amplification section, 5 is a part of a current mirror, and 6 is a current integration section.

7 is a charge/discharge control section.

The differential amplifier section 3 includes a pair of transistors Q3. Q.

The respective emitters of the circuit are connected to current sources IA and IB, respectively, and coupled through a resistor R4.

The reference voltage unit 1 generates a reference voltage for the circuit of the present invention, and the obtained base rst voltage VI is applied to the base of the transistor Q of the differential amplifier unit 3.

The differential amplification input section 4 connects the source voltage Vcc to the resistor R1°R1
The 9-divided voltage point voltage 2 is applied to the base of the transistor Q of the differential amplifier section 3.

As a result, the transistor Q of the differential amplifier section 3.

In the collector of , there is a current according to the voltage difference between V, , and VzO ■2
flows.

Transistors Q4 and Q provided at the collector of Q are part of a current mirror section 5 in the oscillation circuit of FIG. 2, which will be described later.

In the configuration of the oscillation circuit shown in Figure 2, the current mirror part 5
The base of transistor Q is connected to the base and collector of transistor Q4 of the constant current circuit in FIG.
produces a constant collector current I4 approximately equal to the constant current I2 flowing through Q. This collector current ■4 flows into the capacitor C0 of the current integrating section 6 as a charging current,
Terminal voltage■. increases over time.

The charge/discharge control section 7 includes a switch SW provided in parallel with the capacitor Co, and! It is equipped with a pressure detection circuit D1.

The voltage detection circuit is the terminal voltage of capacitor C6. is monitored, and when vo rises due to charging and exceeds a certain voltage, the SW is turned on to discharge the capacitor, and as a result, ■. When S decreases to below a certain other voltage, S
Turn OFF W to stop discharging and restart charging.

As a result, charging and discharging of the capacitor C0 are repeated, resulting in (■). becomes a sawtooth wave that changes at a constant period, and one oscillation output is obtained.

[For production]

First, the first rj! The change in the collector current It with respect to the change in the power supply voltage Vcc in the operation of the constant current circuit of J will be explained. When the value of the power supply voltage Vcc is v4, the voltage dividing resistor of the differential amplification input section 4 is set so that the input voltage z of the differential amplification section 3 is equal to the constant voltage 1 of the output of the reference voltage section 1. R,,R, is adjusted. At this time, for Q,,Q,, I,=1□,■=■2, so the current I, flowing through R4 is 0.

Next, the power supply voltage increases, and Vcc=Vs(>V
In a), V, > V, so It increases,
■.

decreases, and L flows from the ■ side to the ■1 side.

Also, the power supply voltage decreases, Vcc=Vs(<
When V a), V<V, so Vcc=V
4, ■2 decreases, ■ increases, and ■ flows from the vA side to the V side.

In other words, when Vcc increases with Vcc-Vn as the boundary, 1
8 increases, and when Vcc decreases, ■□ also decreases, and the third
The characteristics shown in the figure are obtained. The slope of this curve is R4
It changes depending on the value of , and the larger R4 is, the smaller it is.
The smaller R4 is, the larger I becomes, as shown in FIG.

Next, the operation of the oscillation circuit shown in FIG. 2 will be explained.

The two detection voltages of voltage detection circuit D1 are ■S1+ ■5t
When (V□>Vsz), the voltage detection circuit D1 is.

■ While charging C0. >V, turn switch SW to O.
Turn it to N to start discharging the charge of C8, and when vo<V, turn off the SW to stop the discharge.

Restart charging.

Therefore, the larger the charging current I4 to C0, the more
Repeated discharge cycles become faster. 4 ('ild increases as Vcc increases, so the 1 oscillation frequency f changes linearly in high and low directions according to the vertical changes in Vcc.

FIG. 5 shows the output waveform of this oscillation circuit, and FIG. 6 shows the relationship between Vcc and f. When VCC-V4, f=f,
, when Vcc=Vs, f−f.

Furthermore, if it is desired to change the width of the variation range of f, the constant current value of the constant current source section 2 shown in FIG. 1 may be changed.

If you want to change the slope of f, increase R1 (the slope will become smaller), decrease Ra (the slope will become thicker), and the characteristics of VccflSII will be as shown in Figure 7. .

If you want to expand the variation range of f, change In, Is to I'
If you make it thicker like A (>Ia) or I's (>Im), you get VCC-1! The characteristics of the relationship are as shown in FIG. 8, and the current change expands from ΔI to ΔI2. The resulting Vcc-f relationship is as shown in Figure 9, where Vcc=Va, f corresponding to Vcc''V5 is f4→r'4.fs→'', and the 9 frequency range is Δf, to Δf2.

〔Example〕

The present invention will be explained in detail using FIGS. 10 to 18.

The first embodiment shown in FIG. 10 has a mechanism to shift the frequency change range with respect to Vcc, and the capacitor C
An additional constant current applying section 8 for 0 is provided.

This constant current applying section 8 has a constant current source Ic on the base-collector connection side of the transistor Qs, and uses a current mirror circuit composed of the transistors Q and Q to
A current approximately equal to I flows through the collector of 14 = I
Let z +lC. In other words, I is raised by Ic.

FIG. 11 shows the characteristics of the shifted Vcc-14 relationship with the charging/discharging control section 7 removed from FIG. 10.

The change range of I4 with respect to VCC change is ΔI, to ΔI
It can be seen that it is shifted to 4.

In addition, Fig. 12 shows that as a result, the frequency change range is Δ
This indicates a shift from f3 to Δf4.

This makes it possible to limit the lower limit of the frequency to a certain constant value.

The second embodiment circuit shown in FIG. 13 is for adjusting the ratio of the rise and fall times of a single oscillation output waveform, and includes a constant current source (2) in series with the switch SW of the charge/discharge control section 7. (■.＝
n-1a, 1/n ・+4. n is a natural number),
When the SW is ON, the discharge current passing through the SW is set to be n times or 1/n times the charging current I4 to 00.

FIG. 14 shows the oscillation output waveform of a triangular wave. This triangular wave is 1. -2・I4.

This is convenient for generating a clock with a duty of 5 Q%.

The third embodiment circuit shown in FIG.
Transistors QI and Qz in Figure 1, which is a combination of the circuits shown in each example, use the junction voltage between their respective bases and emitters as a constant voltage source, and these transistors are connected via resistor R1. A bias current is passed through Q, , Q, and the obtained reference voltage 1 is applied to the base of transistor Q3. Further, the transistor Q has an operating function as a switch SW, and also has a Schmitt circuit D.
2 performs an operation of converting a triangular wave into a rectangular wave by its waveform shaping action with hysteresis characteristics.

V when Dt and Q are removed from the circuit in Figure 15
The characteristics of the cc-14 relationship are shown in Figure 16, where Dx,
The operation when Qq is added is as follows. Dz is 2
Two threshold values S, SL (S.

>SL), and when VO>SN, the output Fout
Jump the voltage to ■. As a result, Q is ON
, the charge on C0 is discharged at Io (-214), and ■. gradually decreases, but the voltage of the output Fout is ■. It remains as it is.

Subsequently, when VO<SL, D2 jumps in the opposite direction, sets the voltage of the output Fout to V, and turns Q off. This stops the discharge of C0.

Charging by I4 is resumed. Then, the output Fout is held at VL until vo>S.

Figure 17 shows VCC and output Fout in the circuit of Figure 15.
This is the Vcc-f characteristic showing the relationship between the frequency f of the 18th
The figure shows the waveform of the output Fout. duty as shown
=5Q% square wave pulses can be obtained continuously.

These embodiment circuits are suitable for monolink ICs and can be easily integrated into a single chip.

〔Effect of the invention〕

The present invention makes it possible to smoothly change the current value of a constant current circuit and the oscillation frequency of an oscillation circuit by following fluctuations in power supply voltage in a small, low-power device such as a notebook computer, and the amount of hardware required is It is possible to significantly reduce power consumption and, as a result, improve reliability and reduce costs.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of a constant current circuit according to the present invention. Fig. 2 is a basic configuration diagram of an oscillation circuit according to the present invention. Fig. 3 is an explanatory diagram showing the Vcc-1t* characteristic in Fig. 1. An explanatory diagram showing changes in the slope of the Vcc It characteristic in FIG. 3, FIG. 5 is a waveform diagram of the output of the oscillation circuit in FIG. 2, and FIG. 6 is an explanatory diagram of the Vcc-f characteristic of the circuit in FIG. 2. FIG. 7 is an explanatory diagram of the VCc-f characteristic corresponding to FIG. 2, FIG. 8 is an explanatory diagram of the enlarged VCCIt characteristic of the circuit in FIG. 2, and FIG. Explanatory diagram of f characteristics, 10th
11 is an explanatory diagram of the shifted Vcc Ia characteristics in FIG. 10, and FIG. 12 is a diagram of the shifted Vcc Ia characteristic corresponding to FIG. 11.
-f characteristics, FIG. 13 is a configuration diagram of the second embodiment circuit of the present invention, FIG. 14 is an oscillation output waveform diagram of the second embodiment circuit, and FIG. 15 is a diagram of the third embodiment circuit of the present invention. A configuration diagram of an example circuit,
FIG. 16 is an explanatory diagram of the Vcc 1g characteristic of the circuit of the third embodiment, and FIG. 17 is an explanatory diagram of the Vcc - Fo of the circuit of the third embodiment.
u is an explanatory diagram of frequency characteristics, and FIG. 18 is a waveform diagram of the output Fout of the third embodiment circuit. In FIGS. 1 and 2. 1: Reference voltage section 2: Constant current source section 3: Differential amplification section 4: Differential amplification input section 5: Current mirror section 6: Current integration section 7; Charge ti! 1I7at section Q, ゞQ&: Transistor R, ~R4: Resistor Co: Capacitor ■^, 1 wealth: Constant current source,: Voltage detection circuit SW: Switch

Claims (5)

[Claims] (1) First and second two transistors (Q_3, Q
The emitters of _5) are connected by a resistor (R_4), and
The base of the transistor (Q_3) is connected to the constant voltage source (1), the base of the second transistor (Q_5) is connected to the voltage dividing point of the power supply voltage, and the second transistor (Q_5) is connected to the constant voltage source (1).
) is a constant current circuit whose collector current is controlled at a constant current according to the magnitude of the power supply voltage. (2) Connect a charging/discharging capacitor and the emitters of the first and second transistors, each of which has a constant current source connected to its emitter, with a resistor, and connect the base of the first transistor to a constant voltage source. a charging circuit for the capacitor using a constant current circuit in which the base of the second transistor is connected to a voltage dividing point of the power supply voltage, and the collector current of the second transistor is controlled at a constant current according to the power supply voltage; and a discharge switch circuit provided in parallel with the capacitor; the switch circuit is made conductive when the terminal voltage of the capacitor reaches a certain set value and is made non-conductive when another set value is reached. An oscillation circuit equipped with a charge/discharge control section. (3) Claim 2 is characterized in that the oscillation frequency range is made variable by changing the current value of a current source connected to each emitter of the first and second transistors in the constant current circuit. oscillation circuit. (4) The oscillation circuit according to claim 2, characterized in that a constant current source that can control the current value independently of the constant current circuit is connected to the capacitor, thereby making it possible to shift the range of the oscillation frequency. (5) In claim 2, a constant current source having a current value n times or 1/n times as large as the charging current to the capacitor is provided in the discharging switch circuit provided in the serial number of the capacitor. An oscillation circuit characterized in that it oscillates a triangular wave whose rise and fall time ratio can be varied by inserting the waveform.